Art of removing lead from ferrous articles



. as above Patented Nov.

UNITED STATES OHARLIN L. MANTELL, OF BROOKLYN NEW YORK, ASSIGNOR T0DUDZEELE CORPORA- TION OF AMERICA, OF NEW YORK, N. Y., A CORPORATION OFDELAWARE ART OF BEHOVING LEAD FROM FERBOUS ARTICLES 80 Drawing.Application filed March 29, 1929, Serial No. 351,131.

My invention relates to the art of removing coatings of lead or leadalloys from tubes or other ferrous articles, such as tere plate, scrap,rods, wire, etc.

Broadly, the invention consists in removing the lead coating bysubjecting the art cle (as by immersion) to a solution contain ngappreciable amounts of chlorides and hydrogen ions resulting from theuse of a nonoxidizing mineral acid with a small amount of a catalyticmaterial such as nickel, salts; for example, chloride or sulphate ofmckel.

Lead is one of the best known metals entployed as a material ofconstruction for corrosion resistance. Its use in the manufacture ofsulphuric acid and in the chemical mdustries is well known. It is quiteresistant to many forms of chemical attack. The invention aims to removelead or lead alloys from articles by subjecting them to a solution whichattacks and removes or enables the removal of the lead withoutconsiderable or objectionable attack upon the ferrous article. Theemployment of a catalyst such referred to materially expedites or speedsup the reaction upon the lead coating and thus by reducing the time ofsub ect1on of the article to the deleading bath, reduces the corrosioneffect upon the main body of the article.

In carrying out the process in one approved way, the tubes or otherarticles to be deleaded are first cleaned in an alkaline solution, suchas sodium hydroxide, at a temperature preferably near the boiling point;or heated aqueous solutions of so-called commercial cleaners may beemployed, or alkali solutions with emulsifying agents such assulphonated 011s, and various detergents (as sodium carbonate, phoshates, etc.) e

Af fier cleaning, the 2111710168 are immersed in the deleading solutionin the same general manner or method which is employed in picklingrolled or drawn steel articles.

A preferred deleading solution, as generally described, comprisesappreciable amounts of chlorides and hydrogen ions resulting from theuse of a non-oxidizing mineral acid.

with a small amount of a catalyst, such as nickel salts,

or equivalent.

Renewed March 14, 1932.

As a specific example of one approved solution, t 0 followingingredients and proportions are stated:

Sodium chloride (common salt) in concen trations from about 15% ofweight up to saturation, acidified by approximately 5% sulphuric acid,and as a catalyst, a nickel salt, such as chloride or sulphate ornickel, in concentrations from as low as one one-thousandth stituted forthe sulphuric acid, the sulphuric being preferred in commercial workbecause it is a cheaper reagent.

In plant operation it is desired that the solution shall Work upon andremove the lead without marked effect on the ferrous metal or alloycomposing the main bulk of the fabricated article. The addition ofnickel salts to the bath has been found markedly to speed up thereaction, and thus to reduce attack up on the ferrous body. The bath isdesirably maintained at a temperature from 180 F. up to the boilingpoint of the solution.

After removal from the deleading bath the articles are washed,preferably in hot water, to dissolve and wash off any lead chloride orlead salts still adhering.

The time-required for deleading is a function of the size of thearticle, the thickness of the coating, and the surface finish desired.

Soluble platinum salts may be used in low concentrations in place ofnickel salts, but are usually unavailable for this purpose because ofthe higher cost. Accordingly, wherever I refer in the claims thecatalyst, I mean any material which is substantially the equivalent ofnickel salts in the sense that it will bring about to a practical-extentthe results herein attributed to the presence of nickel salts. It isbelieved to nickel salts as ing appreciable amounts that the catalyticaction of the nickel salt is as follows The nickel ions are precipitatedas nickel atoms on the surface of the lead to form a nickel leadelectrolytic couple, as the result of which the attack on the lead andits resultant solution is accelerated.

The present invention is an improvement upon that disclosed in my priorapplication, Serial No. 325,643, filed December 12, 1928, and consistslargely in the addition to certain typical deleading solutions thereindisclosed, of a catalyst of the character and for the purposes abovedescribed.

I claim:

1. A deleading solution containing appreciable amounts of chlorides andhydrogen ions resulting from the use of a non-oxidizing mineral acid,with a small proportion of a nickel salt as a catalyst.

2. A deleading solution containing sodium chloride in concentrationsfrom approxmate- 1y 15% by weight up to saturation, and approximately 5%non-oxidizing mineral acid, and a nickel salt as a catalyst inconcentrations from approximately 1000th of 1% to approximately of 1%.

3. A deleading solution containing sodium chloride concentrations fromapproximately 15 by weight up to saturation, and approximately 5% as acatalyst in concentrations from approxirpagly 1000th of 1% toapproximately 0 1 o.

4. A deleading solution containing sodium chloride in concentrationsfrom approximately 15% by weight up to saturation, and approximately 5non-oxidizing mineral acid, and a nickel salt in small percentage as acatalyst.

5. A deleading solution containing sodium chloride concentrations fromapproximately 15% by weight up to saturation, and approximately 5%sulphuric acid, and a nickel salt in relatively low concentration as acatalyst.

6. A deleading process including, as a characteristic operation,subjecting a leadcoated ferrous article to a solution comprisingappreciable amounts of chlorides and hydrogen ions resulting from theuse of a non-oxidizing mineral acid, with a small proportion of a nickelsalt as a catalyst.

7 A deleading process including as a. characteristic operationsubjecting a lead coated ferrous article to a solution compris ingsodium chloride in concentrations from approximately 15% by weight up tosaturation, and approximately 5% non-oxidlzing mineral acid, and anickel salt as a catalyst in concentrations from approximately 1000th of1% to approximately of 1%.

8. A deleading process including, as a characteristic operation,subjecting a leadcoated ferrous article to asolution comprissulphuricacid, and a nickel salt of chlorides and hydrogen ions resulting fromthe use of a non-oxidizing mineral acid, with a small roportion of anickel salt as a catalyst, the ath being maintained at a temperaturenear boilmg.

9. A deleading process including, as a characteristic operation,subjecting a leadcoated ferrous article to a solution comprisingappreciable amounts of chlorides and hydrogen ions resulting from theuse of a non-oxidizing mineral acid, with a small proportion of a nickelsalt as a catalyst, the bath being maintained at a temperature fromapproximately 180 F. to boiling.

10. A deleading process including as a characteristic operationsubjecting a lead coated ferrous article to a solution comprisingappreciable amounts of chlorides and hydrogen ions resulting from theuse of a non-oxidizing mineral acid, with a small proportion of a nickelsalt as a catalyst, the bath being maintained at a temperature nearboilin 11. The described process, including as characteristic features,cleaning lead-coated ferrous articles in an alkaline solution,subjecting them to a deleading bath of character described in claim 1,and washing the articles to remove remaining lead and deleadingsolution.

12. The described process including as characteristic features, cleaninglead-coated ferrous articles in an alkaline solution, subjectin them toa deleading bath of character descri ed in claim 2, and washing thearticles to remove remaining lead and deleading solution.

13. A deleading solution containing appreciable amounts of chlorides andhydrogen ions, with nickel salt as a catalyst.

In testimony whereof I aflix my s 'i%ature.

CHARLES L. MAN LL.

